Attempts will be made to prove whether IgE is essential for histamine release from mast cells. The antibody against receptors for IgE will be prepared using basophilic leukemia cells. Experiments will be undertaken to study whether the reaction of anti-receptor antibody with the receptor on normal mast cells may include histamine release. Infection of rats with Nippostrongylus brasiliensis induces proliferation of IgE-bearing lymphocytes and potentiates IgE production. Based on these findings, cellular events as well as possible humoral factors involved in the response, will be studied. BIBLIOGRAPHIC REFERENCES: W. Konig and K. Ishizaka. Binding of rat IgE with the subcellular components of normal rat mast cells. Immunochemistry, 13: 345, 1976. T. Ishizaka, H. Okudaira and K. Ishizaka. Development of rat mast cells in vitro. I. Differentiation of mast cells from thymus cells. J. Immunol., 116: 747, 1976.